Other authors discount only the first book and all the rest are the same price. (mybookcave.com)
Legitimate presses will never make an author commit to purchasing any copies of the work (though often they do offer authors a discount on copies the author elects to buy). (rmfw.org)
They give authors a discount price, typically 30 percent off but negotiable up to 40 percent on carton quantities. (janefriedman.com)